Preformed concrete panels are a popular and economic method of constructing a variety of structures. Of particular interest are composite concrete panels. Composite concrete panels are most often manufactured and used for thermal insulation purposes. Typically a composite panel is comprised of three layers, a middle insulation layer and two outer concrete layers or wythes which sandwich the middle insulation layer. Walls of this type are often called sandwich walls. The insulation layer often consists of a 3 inch Styrofoam® sheet. Generally, one of the concrete layers in the composite panel is substantially thicker than the other. In a typical composite panel the three layers are generally only held together with steel bar anchors.
Typical composite panels have two major disadvantages. First, they have a very small shear resistance. Most of the shear of a typical sandwich panel occurs in the middle third of the panel where the insulation layer lies. Because the insulation layer has nearly no shear resistance this makes typical composite panels susceptible to shear failure. The second disadvantage of typical composite panels is that they cannot be used in load bearing and structural applications.
In recent years, fiber reinforced polymer (FRP) composites have emerged as an alternative to traditional materials for strengthening of various structures. The light weight of the material, high-strength to weight ratio, corrosion resistance, and high efficiency of construction are among many of the advantages of this material. Efforts have been made by some researchers to use FRP bars to reinforce composite panels by either replacing the steel with FRP bars or by attempting to use FRP bars to produce a truss-like action inside the composite panel. Unfortunately, these efforts have failed to satisfactorily increase the shear resistance capability or axial load capacity of the composite panel. As such, methods and systems for increasing shear resistance capability and axial load capacity of composite wall panels continues to be sought.